The Wadsworth Center's Resource for the Visualization of Biological Complexity (RVBC) employs three-dimensional (3D) electron microscopy at different levels of resolution to study cell processes in the native context and at close-to-native conditions, and to capture the hierarchical organization of living matter. (i) Low-dose cryo-tomography of frozen-hydrated cell and tissue sections will be further developed by utilizing novel techniques such as ion beam milling, through a collaboration with SUNY Albany, to reduce cutting artifacts. Efforts will be made to optimize data collection, alignment, and reconstruction to achieve a range of resolution where molecular signatures can be recognized. (ii) Macromolecular interactions will be studied as dynamic processes by 3D cryo-imaging of complexes in single-particle form and by development of time-resolved imaging methods, using the rich test bed provided by in-house projects such as the ryanodine receptor and the ribosome. In addition to spray-freezing and use of UV-activated caged compounds, we will explore the use of novel nanofabrication methods in designing EM grids, in a consortium agreement with the Rensselaer Polytechnic Institute, that can act as mixing platforms. (iii) Heterogeneity is recognized as the single biggest remaining obstacle to the achievement of higher resolution in single-particle reconstruction of macromolecular assemblies. General methods of supervised and unsupervised classification will be developed in collaboration with lead experts, using both phantom and experimental data sets that represent typical problems encountered in the field. In addition to advancing these three areas of technological and research development, which are driven by research at the Wadsworth Center and outside collaborations, we continue to offer the unique facilities of the Resource to the Biological Community in service projects.